Blizzard have announced that Season of Mastery characters will be able to transfer to either Classic Era or Wrath of the Lich King Classic when the season ends!
Som Transfer (Source)
Since the very beginning of Season of Mastery the topic of where seasonal characters would end up when the season ends has been a hot topic of discussion for not only the community, but for our team internally as well. We’ve spent a ton of times talking amongst ourselves, talking to SoM players, and reading comments on these forums and social media, and it’s very clear that there’s a strong desire to be able to continue the adventures of your seasonal characters in Wrath of the Lich King Classic. We are excited to let everyone know that there will be a way for Season of Mastery characters to transfer to either Classic Era or Wrath of the Lich King Classic for free when the current season begins to wind down.
It’s likely you’ll have questions around this, and we hope to be able to share more details soon. As for timing, this is still quite a ways off and will happen sometime well after the release of Naxxramas in SoM. We want to make sure that Naxxramas has plenty of time to breathe before we start this process and players start to find their new forever homes for their seasonal characters.
Thanks a ton for all of the feedback on this.